It's holiday party season, and etiquette landmines abound, between the abundant buffets, free-flowing booze and potential for wardrobe faux pas. Twin Cities–based manners expert Juliet Mitchell, who runs the Life Etiquette Institute, has seen and heard of all sorts of guest mishaps, including employees who have lost jobs by overdoing it at the company party's open bar.

Planning ahead and understanding the host's perspective helps promote appropriate behavior, Mitchell says. She shares her list of the top 10 mistakes party guests make — and tips for how to avoid them.

1. Failing to RSVP

It's important to let the party host know if you plan to attend or not, Mitchell says, as the headcount drives planning for everything from seating to food. Make sure to check who is included in the invitation and don't bring uninvited guests. If you know the host well, you can call and ask for an exception. "But you certainly don't want to put any extra stress on the host," Mitchell notes. If you're unsure of your ability to attend, responding with a "maybe" is better than not responding at all.

2. Arriving too early, too late, or staying too long

It's okay to arrive early if you ask the host ahead of time and offer to lend a hand. Otherwise, showing up while the host is attending to last-minute details can be an imposition. Better to pop into a nearby coffee shop or sit in your car for a few moments, Mitchell suggests. If you do enter early, make it clear to your host that you don't need to be entertained. And always be on time for programmed events — late-arriving wedding guests have been known to miss the entire ceremony, Mitchell says .

If the invitation lists an end time, prepare to leave then, unless the host encourages you to stay longer. "If the host says, 'I'm so glad you came, it's been great.' Then start walking to the door," Mitchell advises. "And 'Let's get together again soon' means, 'This party is over.'" You can offer to stay late and clean up, but the host may not want people around if they've already expended a lot of energy preparing for the party and entertaining guests.

3. Whining or complaining

If you had a long drive to get to the party, struggled to park, or don't like the food, avoid airing such complaints. "All of that just puts a damper on things and makes people uncomfortable," Mitchell says. "If you're going to go, get your mind and spirit ready. If you accept the invitation, show genuine appreciation for whatever it is."

4. Failing to thank the host

If nothing else, try to thank the host on the way out. But it's best to also express your gratitude afterword. Texting is okay, or, if the host used a digital invitation, you can send a message through the app. You can also always call, email, or send a handwritten note. "The paper card — they're still selling them — it's still a great option," Mitchell notes.

5. Not dressing appropriately

If the host specifies a dress code, stick to it. If you don't want to wear a tuxedo, for example, Mitchell says you should consider turning the invitation down before showing up in jeans. "The person has been planning the type of atmosphere they want, so, to me, it's an affront to the host to just wear what you want," she says. "Respect their wishes, or respectfully decline." If you're unsure about to what to wear, you can look up dress-code terms, ask the host, or the venue. And err on the side of dressing more conservatively. "If you overdress and layer, sometimes you can take it down a notch, but if you are underdressed, it's hard to take it up a notch," Mitchell says.

6. Overindulging in food or drink

Hosts want guests to enjoy the food and drink, but a party's focus should be socializing. If you think you'll be tempted to park yourself in front of the buffet, have a snack beforehand, Mitchell advises. "I tell people, this is one time you can go low and not high. In other words, don't pile your plate." She suggests going into the event with a drink limit in mind. Many etiquette professionals suggest having one drink, or abstaining.

7. Ignoring personal boundaries

Overindulging in alcohol can loosen inhibitions and cause partygoers to overstep personal boundaries: talking too loudly, saying inappropriate things or invading people's personal space. In a professional setting, if these behaviors don't cause you to lose your job, they will likely cause your colleagues to view you differently. If someone takes a conversation into uncomfortable territory, Mitchell recommends telling them you don't want to discuss the subject and then pivoting to a new topic or excusing yourself.

8. Using devices excessively

Resist the urge to be on your phone. "Make sure you're working on your social engagement and interpersonal skills, so that you can be in conversation with people," Mitchell says. If you're taking pictures, make sure people want to be in your picture. Tell people if you plan to post the photos on social media.

9. Not introducing yourself or others

People often get uncomfortable trying to enter conversations or invite others into a group. In her etiquette classes, Mitchell conducts exercises that replicate a social gathering, so students can practice bringing others into a conversation circle. "When someone comes up, take the lead in introducing that person," she says. "Or if you're that person, and you see it's not happening, go ahead and take the lead and introduce yourself."

10. Forgetting to bring cash

Always bring a little cash to a party venue, Mitchell advises, so you can tip parking attendants, coat check staff, or bartenders.